Introduction to Sophora japonica Varieties: Characteristics of Common Cultivars and Their Landscape Applications

Sophora japonica (Japanese pagoda tree) is a deciduous tree of the genus Sophora in the Fabaceae family. It originated in China and has a long history of cultivation, and it is a commonly used street tree and shade tree in northern regions. The tree is tall, with a broad crown, alternate pinnately compound leaves, yellow-white pea-like flowers in late summer, and bead-like fleshy pods. It is drought-tolerant, cold-tolerant and tolerant of poor soil, has a certain resistance to smoke, dust and harmful gases, and is long-lived; ancient pagoda trees can often be seen in both urban and rural areas.

Through long-term cultivation, Sophora japonica has developed quite a few ornamental cultivars, among which the common ones include the dragon-claw pagoda tree (Sophora japonica var. pendula), the golden-branch pagoda tree, the golden-leaf pagoda tree (Sophora japonica 'Jinye') and the five-leaf pagoda tree. The dragon-claw pagoda tree has twisting, drooping branches and a crown shaped like an umbrella; it is mostly propagated by grafting onto seedling rootstock of Sophora japonica, and is suitable for placing at courtyard entrances and in a corner of the lawn. The current-year branches of the golden-branch pagoda tree turn golden yellow in autumn and winter, and the golden-leaf pagoda tree has bright golden-yellow foliage; both are widely used colored-leaf trees. The leaflets of the five-leaf pagoda tree often cluster together and resemble butterflies, so it is also called the butterfly pagoda tree, with a very distinctive form.

Sophora japonica has a wide range of uses: it can serve as a street tree or shade tree, and can also be used for greening around homes and for shelterbelt planting. Its flowering period produces a large quantity of flowers, making it an important nectar plant in summer and autumn; the dried flower buds are the traditional Chinese medicinal material huaimi; and the wood has straight grain and can be used in construction and furniture making.

When planting Sophora japonica, choose a site with ample sunlight and good drainage. Transplanting before spring bud break or after leaf fall in autumn gives a higher survival rate; for large saplings, a proper root ball must be kept and the branches and leaves pruned moderately. Sophora japonica is easily confused with black locust (Robinia pseudoacacia), also called false acacia, which blooms white flowers in spring and has stipular thorns on the twigs; Sophora japonica blooms yellow-white flowers in summer and has no stipular thorns, so the two can be distinguished on this basis when buying. In daily care, prune in good time to keep the crown neat, and pay attention to controlling common pests such as aphids and inchworms, and the tree will grow vigorously.